Abstract: A field strength indicator for a magnetic particle inspection process is used to determine field strength and direction sufficient to identify real flaws in a test piece. The field strength indicator is a substantially flat shim having at least one series of artificial flaws formed therein by electric discharge machining. The artificial flaws have a geometry which render them compatible with real flaws and thus enable the magnetic field strength and direction to be properly set for conducting a magnetic particle inspection procedure. The surface containing the artifical flaws must be covered with a thin inert and non-magnetic coating for proper operation.

Abstract: A ventilation system for a motor vehicle includes an air intake opening through a wall of the vehicle and an air scoop to direct air thereinto, the intake opening being the only deliberate air permeable opening in the vehicle. A filter bag is connected to the air intake via a conduit, such that all air entering the vehicle through the intake opening is filtered of dust by the filter bag. Clean intake air is thereby used to generate a positive pressure in the vehicle which prevents the infiltration of dust and air into the vehicle through incidental cracks and crevices.